Substrate treating apparatus and method for manufacturing semiconductor device

ABSTRACT

A support section ( 28 ) for supporting a wafer ( 1 ) is convexly formed in the center of a receiving section ( 26 ) of a support groove ( 25 ) of a boat  21 . At the time of boat loading of the boat ( 21 ), in which wafers ( 1 ) respectively received by the supporting sections ( 28 ) are aligned, from a standby chamber ( 33 ) to a processing chamber ( 14 ), the pressure in the standby chamber ( 33 ) and processing chamber ( 14 ) is set to  200  pascals or more, and  3000  pascals or less. By supporting the wafer upwards from the receiving section with use of the support section, even if peeling of the film on the wafer occurs from a large frictional force between the supported surface of the wafer and the support section under a reduced pressure, the particles from the peeling are caught by the receiving section and therefore particles are prevented from adhering to the IC fabrication surface of the wafer directly below the receiving section.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/517,765, filed Feb. 3, 2006, which application is a 371 of PCTApplication No. PCT/JP03/08097, filed Jun. 26, 2003, which applicationclaims priority of Japanese Application Nos. 2002-187566, filed Jun. 27,2002 and 2003-084774, filed Mar. 26, 2003, all of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a substrate treating apparatus and amethod for manufacturing semiconductor devices, and relates inparticular to a method for manufacturing semiconductor integratedcircuit devices (hereafter called IC), for example for technologyeffective in processes for depositing doped-polysilicon film ornondoped-polysilicon film, silicon nitride (Si₃N₄) or silicon oxide(SiOx) films with a thermal CVD apparatus on semiconductor wafer(hereinafter called wafer) for fabricating integrated circuitscontaining semiconductor devices.

BACKGROUND ART

The batch mode vertical hot-wall depressurization CVD apparatus iswidely used in IC manufacturing methods in processes for depositing CVDfilms such as doped-polysilicon film or nondoped-polysilicon film,silicon nitride or silicon oxide films on wafers. The batch modevertical hot-wall depressurization CVD apparatus (hereafter CVDapparatus) is made up of a vertically installed process tube comprisedof an inner tube for containing the wafer and an outer tube enclosingthe inner tube, a gas supply tube to feed a film-forming gas in theprocessing chamber formed by the process tube, an exhaust tube forevacuating gas for a vacuum from the processing chamber, a heater unitinstalled outside of the process tube for heating the processingchamber, a boat for loading and unloading of multiple wafers into andout of the processing chamber while holding on a multiple step supportgroove, and a standby chamber for maintaining the boats in standbystatus for loading and unloading to the processing chamber. Aftermultiple wafers are loaded (wafer charging) into the boat in the standbychamber, the boat is loaded (boat loading) from the standby chamber intothe preheated processing chamber, and along with film-forming gas beingsupplied from the gas supply tube to the processing chamber, theprocessing chamber is heated to the specified temperature by the heaterunit so that a CVD film is deposited on the wafer (see for examplePatent document 1).

Boat loading methods for these type of CVD apparatus of the prior artinclude a boat loading method wherein the processing chamber and thestandby chamber are both at atmospheric pressure; a boat loading methodwherein the air in the processing chamber and the standby chamber areboth purged by nitrogen (N₂) gas; and a boat loading method wherein theprocessing chamber and the standby chamber are evacuated to a vacuum.The boat loading method wherein the processing chamber and the standbychamber are both at atmospheric pressure, tends to easily develop anatural oxidized film during boat loading and therefore has the problemthat the oxidized film has adverse effects on the productivity of the ICmanufacturing method. The boat loading method wherein the air in theprocessing chamber and the standby chamber are both purged by nitrogengas successfully suppresses development of the natural oxidized filmcompared to the method for boat loading at atmospheric pressure, howeveroxygen (O₂) cannot be completely eliminated from the nitrogen gas sothat the natural oxidized film increases to a certain extent. The boatloading method wherein the processing chamber and the standby chamberare evacuated to a vacuum can eliminate virtually all of the oxygen sothat an increase in the natural oxidized film is suppressed compared tothe method for boat loading under a nitrogen gas environment.

However it was discovered that particles are generated in boat loadingthat evacuates the processing chamber and the standby chamber to avacuum. In other words, during boat loading of wafers into the preheatedprocessing chamber, the wafer temperature rises from the periphery onthe side near the heater, and rises slower in the center section on thefar side from the heater creating a temperature differential. Due to therelation between this temperature differential within the wafer and thewafer's own weight, the wafer is known to curve into a concave shape.Along with this curvature of the wafer, the support surface of the wafersupport groove on the boat and the supported surface on the periphery onthe lower surface of the wafer rub against each other. When theprocessing chamber and the standby chamber are evacuated to a vacuum atthis time, the frictional force between the boat support surface and thewafer supported surface becomes large so that the film deposited on thelower surface of the wafer in the previous process is peeled away. Thefilm that was peeled away becomes particles and spills downwards fromthe support surface of the support groove. These particles fallingdirectly downward adhere to upper surface of the wafer where the IC isfabricated and therefore badly affect the productivity in the ICmanufacturing method.

The present invention therefore has the object of providing a substratetreating apparatus and a method for manufacturing semiconductor devicescapable of preventing a drop in production due to particles from thesupported surface of the substrate under decompression.

DISCLOSURE OF INVENTION

The present invention is a substrate treating apparatus comprising aprocessing chamber for processing at least one substrate, and asubstrate support member for supporting at least one substrate, aprechamber for storing this substrate support member, and a controldevice for regulating the pressure to a pressure lower than atmosphericpressure during loading from a prechamber into the processing chamber ofthe substrate support member supporting at least one substrate, whereinthe substrate support member contains a support section to be contactedthe substrate, and a receiving section installed below the supportsection and extending outwards from a section of the outer periphery ofthe support section. In this substrate treating apparatus, even iffriction occurs between the supported surface of the substrate and thesupport section of the substrate support member causing peeling of thesubstrate film, the particles generated from the peeling are caught bythe receiving section and therefore prevented from dropping onto thesubstrate so that a decline in substrate production due to peeling ofthe film on the substrate can be prevented.

A method for manufacturing semiconductor devices comprises a step forsupporting at least one substrate on a substrate support membercontaining a support section to be contacted at least one substrate, anda receiving section installed below the support section and extendingoutwards from a section of the outer periphery of the support section; astep for loading the substrate support member supporting at least onesubstrate at a pressure lower than atmospheric pressure into theprocessing chamber; and a step to process at least one substratesupported by the substrate support member in the processing chamber. Inthis manufacturing method for semiconductor devices, even if frictionoccurs between the supported surface of the substrate and the supportsection of the substrate support member causing the substrate film topeel, the particles generated from the peeling are caught by thereceiving section and therefore prevented from dropping onto thesubstrate so that a decline in production due to peeling of the film onthe substrate can be prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a frontal cross sectional view showing the CVD apparatus ofthe first embodiment of the present invention.

FIGS. 2 a and 2 b are drawings of an essential portion after the boatloading step; FIG. 2 a is a frontal cross sectional view; FIG. 2 b is anenlarged cross sectional view of the b section in FIG. 2 a.

FIG. 3 is a perspective view showing the support groove of the boat.

FIG. 4 is a graph showing the interrelation between the shape of thesupport surface and the increased quantity of particles.

FIGS. 5 a and 5 b are drawings showing the particle distribution; FIG. 5a is a drawing showing the case when there is no protrusion; FIG. 5 b isa drawing showing the case when there is a protrusion.

FIGS. 6 a and 6 b are timing charts showing the pressure in the filmforming process of the IC manufacturing method of the first embodimentof the present invention.

FIG. 7 is a perspective view showing the support groove section of theboat for the CVD apparatus of the second embodiment of the presentinvention.

FIGS. 8 a and 8 b are timing charts showing the pressure in the filmforming process for the IC manufacturing method of the second embodimentof the present invention.

FIG. 9 is a graph showing the relation of an increased particle quantityto the size of the receiving section.

FIG. 10 is a drawing comparing the respective receiving sections used inthe experiment in FIG. 9.

FIGS. 11 a and 11 b are drawings showing the particle distribution; FIG.11 a shows the example of the prior art; FIG. 11 b shows the presentembodiment.

FIGS. 12 a, 12 b and 12 c are drawings showing a section of the supportgroove on the boat of the CVD apparatus of the third embodiment of thepresent invention; FIG. 12 a is a perspective view; FIG. 12 b is a plancross sectional view; and FIG. 12 c is a frontal cross sectional view.

BEST MODE FOR CARRYING OUT THE INVENTION

The first embodiment of the present invention is described next whilereferring to the accompanying drawings.

In the present embodiment, the film-forming process of the manufacturingmethod for the semiconductor device of the present invention isimplemented by the CVD apparatus (batch mode vertical hot-walldepressurization CVD apparatus) shown in FIG. 1 and FIG. 2. The CVDapparatus shown in FIG. 1 and FIG. 2 contains a vertical process tube 11disposed vertically with the vertical center line and fixedly supported.This process tube 11 is made up of an inner tube 12 and an outer tube13. The inner tube 12 is made of quartz (SiO₂) or silicon carbide (SiC)and formed in a cylindrical shape. The outer tube 13 is made of quartzor silicon carbide and formed in a cylindrical shape. The inner tube 12is formed with openings at the top and bottom ends formed in acylindrical shape. A processing chamber 14 is formed in a hollow part ofthe inner tube 12 for the multiple wafers carried in while held in aperpendicular array by the boat. A furnace inlet 15 is formed at thelower end opening of the inner tube 12 for loading and unloading ofwafers as the substrates for processing. The inner diameter of the innertube 12 is therefore set to a size larger than the maximum outerdiameter of the wafers being handled. The outer tube 13 is formed in acylindrical shape with the top end sealed and the bottom end open andwith the inner diameter larger than the outer diameter of the inner tube13. The outer tube 13 is formed concentrically to enclose the outer sideof the inner tube 12. A manifold 16 is formed in a ring shape betweenthe bottom end of the inner tube 12 and the bottom end of the outer tube12 for air-tight sealing. The manifold 16 is supported by a casing 31 ofthe CVD apparatus so that the process tube 11 is perpendicularlyinstalled. The bottom end opening of the manifold 16 is opened andclosed by a furnace opening gate valve 29.

An exhaust pipe 17 is connected on the upper section of the side wall ofthe manifold 16 by way of an exhaust line 42 to an exhaust device 41made up of a vacuum pump. A flow rate controller valve 43 and a pressuremeter 44 are installed on the exhaust line 42. The flow rate controllervalve 43 is controlled by a control device 40. The pressure meter 44sends the measurement results to the control device 40. The exhaust pipe17 connects to an exhaust path 18 formed from the gap formed between theinner tube 12 and the outer tube 13. The cross sectional shape of theexhaust path 18 is formed in a circular ring shape with a fixed width bythe gap between the inner tube 12 and the outer tube 13. The exhaustpipe 17 is connected to the manifold 16 and therefore installed at thelowermost end of the exhaust path 18. A gas supply pipe 19 on the lowersection of the side wall of the manifold 16, connects to the furnaceinlet 15 of the inner tube 12. A film-forming gas supply source 50 and anitrogen gas supply source 60 are respectively connected to the gassupply pipe 19 by a film-forming gas supply line 51 and the nitrogen gassupply line 61. A film-forming gas flow rate control valve 52 and anitrogen gas flow rate control valve 62 respectively controlled by thecontrol device 40 are each installed on the film-forming gas supply line51 and the nitrogen gas supply line 61. Gas supplied to the furnaceinlet 15 by the gas supply pipe 19, passes through the processingchamber 14 of the inner tube 12, passes along the exhaust path 18 and isexhausted by the exhaust pipe 17. A seal cap 20 at the bottom edge ofthe manifold 16 that seals the processing chamber 14 makes contact fromthe lower side. The seal cap 20 is formed in a disk shape roughlyequivalent to the outer diameter of the manifold 16, and is raised orlowered perpendicularly by the boat elevator (not shown in drawing).

A boat 21 for supporting a wafer 1 as the substrate for processing issupported upright on the center line of the seal cap 20. The boat 21 iscomprised entirely of quartz or silicon carbide. The boat 21 iscomprised of a pair of end plates 22, 23 on the top and bottom andmultiple holding members 24 (three pieces in the example in the figure)installed vertically between both end plates 22, 23. Many supportgrooves 25 are carved out so as to form openings mutually facing eachother and formed equally spaced longitudinal intervals on each holdingmember 24. As shown in FIG. 2 and FIG. 3, an R chamfer section 27 isformed on the outer circumferential periphery (edge) of a supportsurface 26 formed from the upward facing surface of each support groove25. The curved radius of the R chamfer section 27 is set to onemillimeter or more. A semispherical protrusion. 28 is formed in thecenter of the support surface 26. The outer circumferential section ofthe wafer 1 are inserted in the support grooves 25 at mutually equalsteps on the holding members 24. The multiple points (three points inthe present embodiment) on the periphery of the lower surface of thewafer 1 are received and held by the protrusion 28 on the supportsurface 26. The protrusion 28 therefore comprises a support section tosupport the wafer. In their respective states while held by the supportgrooves 25, the multiple wafers 1 are arrayed while centeredhorizontally on the boat 21.

A heater unit 30 for heating the interior of the process tube 11 isinstalled concentrically on the outside of the outer tube 13 so as toenclose the periphery of the outer tube 13. The heater unit 30 heats theentire interior of the process tube 11 to a uniform or a presettemperature distribution. The heater unit 30 is installedperpendicularly to be supported by the casing 31 of the CVD apparatus.As shown in FIG. 1, the casing 31 is comprised of a heater unit chamber32, and a standby chamber 33 for the boat 21 to await loading orunloading to the processing chamber 14. The standby chamber 33 isconfigured for the load-lock system (a system where an isolation valvesuch as a gate valve is used to isolate the processing chamber and theloading/unloading chambers, prevent the inflow of air to the processingchamber, and reduce disturbances such as from the temperature orpressure in order to stabilize the processing). An exhaust pipe 34 toexhaust the standby chamber 33, and a nitrogen gas supply pipe 35 tosupply nitrogen gas to the standby chamber 33 as the purge gas arerespectively connected to the side wall of the standby chamber 33 of thecasing 31. The exhaust pipe 34 is connected to an exhaust device 41 byway of an exhaust line 45 to which a flow rate controller valve 46 and apressure meter 47 are installed. The flow rate controller valve 46 isregulated by the control device 40. The pressure meter 47 sends themeasurement results to the control device 40. The nitrogen gas supplypipe 35 is connected to a nitrogen gas supply source 60 by way of anitrogen gas supply line 63 to which a flow rate controller 64 isinstalled. The flow rate controller valve 64 is regulated by the controldevice 40. A wafer loading/unloading opening is formed to be opened andclosed by the gate valve on the other sidewall of the standby chamber33. A boat elevator (not shown in drawing) is installed in the interiorof the standby chamber 33 to raise and lower the seal cap 20.

The film-forming process for the IC manufacturing method of oneembodiment of the present invention using the above-mentioned CVDapparatus when forming a doped polysilicon film on the wafer isdescribed next.

In the wafer charging step where multiple wafers 1 are loaded into theboat 21, as shown in FIG. 1, with the boat 21 in standby in the standbychamber 33 the multiple wafers 1 are loaded into the boat 21 by thewafer transfer equipment. The air in the standby chamber 33 is purged atthis time by nitrogen gas supplied from the nitrogen gas supply pipe 35.In other words, the control device 40 regulates the gas flow ratecontrol valve 64 so that nitrogen gas from the nitrogen gas supplysource 60 is supplied to the standby chamber 33 from the nitrogen gassupply pipe 35 via the nitrogen gas supply line 63. As shown in FIG. 6a, the pressure in the standby chamber 33 is maintained at atmosphericpressure (approximately 1013 hPa). This nitrogen gas purging of thestandby chamber 33 prevents the generation of a naturally oxidized filmon the wafers 1, and allows the wafer charging operation to beimplemented under atmospheric pressure. The furnace opening gate valve29 is closed at this time.

In the boat loading step where the boat 21 installed with a specifiednumber of multiple wafers 1 is loaded into the processing chamber 14,after the furnace inlet 15 is opened by the furnace gate valve 29, theboat 21 is raised by the boat elevator, and is loaded from the furnaceinlet 15 of inner tube 12 to the processing chamber 14. As shown in FIG.2, the boat 21 is positioned in the processing chamber 14 while stillsupported by the seal cap 20 that seals the furnace inlet 15. Duringthis boat loading, nitrogen gas is continually supplied from thenitrogen gas supply pipe 35 and the gas supply pipe 19 so that thepressure in the standby chamber 33 and the processing chamber 14 arerespectively 200 Pa, and is respectively exhausted by the exhaust pipe34 and the exhaust pipe 17. In other words, the control device 40controls the nitrogen gas flow rate control valve 64 so that the flowrate of nitrogen gas from the nitrogen gas supply pipe 35 to the standbychamber 33 is regulated, and controls the flow rate control value 46 sothat the standby chamber 33 is exhausted. As shown in FIG. 6 a, thepressure in the standby chamber 33 is depressurized to 200 Pa andmaintained. The control device 40 also controls the flow rate controlvalve 62 so that the flow rate of the nitrogen gas from the gas supplypipe 19 to the processing chamber 14 is regulated, and controls the flowrate control valve 43 so that the processing chamber 14 is exhausted. Asshown in FIG. 6 b, the processing chamber 14 is maintained at a pressureof 200 Pa. The furnace opening gate valve 29 is closed at this time andthe furnace inlet 15 is sealed air-tight. The temperature of theprocessing chamber 14 is regulated to maintain the heat processingtemperature (for example 530° C.). In this state, or in other words astate where the pressure of the standby chamber 33 and the processingchamber 14 have become equal, the standby chamber 33 and the processingchamber 14 are connected by opening the furnace opening gate valve 29,and boat loading is performed at a pressure of 200 Pa.

In the processing step in processing chamber 14 for processing thewafers 1 held by the boat 21, nitrogen gas continually flows from thegas supply pipe 19 so that the interior of the processing chamber 14 ismaintained at the specified vacuum intensity (110 Pa), and is exhaustedvia the exhaust pipe 17. The control device 40 in other words, regulatesthe flow rate of nitrogen gas from the gas supply tube 19 to theprocessing chamber 14 by controlling the nitrogen gas flow rate controlvalve 62. The control device 40 also exhausts the processing chamber 14by regulating the flow rate control valve 43. As shown in FIG. 6 b, theprocessing chamber 14 is depressurized to 110 Pa. The process gas 36 isnext supplied to the processing chamber 14 via the gas supply pipe 19for depositing a doped polysilicon film 2 as the specified film on thesurface of the wafer 1 by the thermal CVD method. In other words, thecontrol device 40 regulates a film-forming gas flow rate control valve52 to supply monosilane (SiH₄) gas and phosphine (PH₃) gas as a processgas 36 to the processing chamber 14 via the gas supply pipe 19. Thissupplied process gas 36 rises in the processing chamber 14 of the innertube 12, flows out from the opening in the upper end, through theexhaust path 18 formed by the gap between the inner tube 12 and theouter tube 13 and is exhausted from the exhaust pipe 17.

When the preset processing time has elapsed, along with the seal cap 20lowering and the furnace inlet 15 of processing chamber 14 opening, thewafer 1 group supported in the boat 21 is unloaded (boat unloading) tothe external section of the process tube 11 from the furnace inlet 15.In this boat unloading step, as shown in FIG. 6, the pressure of theprocessing chamber 14 is increased to 200 Pa, approximately the same asthe pressure in the standby chamber 33 maintained at 200 Pa. In otherwords, the control device 40 regulates the flow rate of nitrogen gasfrom the gas supply tube 19 to the processing chamber 14 by controllingthe nitrogen gas flow rate control valve 62, and regulates the flow ratecontrol valve 43, as shown in FIG. 6 b, to increase and maintain thepressure of the processing chamber 14 at 200 Pa. Performing the boatunloading step at a low pressure such as 200 Pa is extremely effectivein preventing the formation of a natural oxidized film on the wafer 1that has been processed.

In the wafer discharging step where the processed wafer 1 is removedfrom the boat 21 that was unloaded in the standby chamber 33, as shownin FIG. 6 a, the air in the standby chamber 33 is purged by nitrogen gassupplied from the nitrogen gas supply pipe 35. In other words, byregulating the nitrogen gas flow rate control valve 64 with the controldevice 40, nitrogen gas from the nitrogen gas supply source 60 issupplied from the nitrogen gas supply pipe 35 to the standby chamber 33via the nitrogen gas supply line 63. As shown in FIG. 6 a, the pressurein the standby chamber 33 is increased to atmospheric pressure and ismaintained there. The processed wafer 1 that has reached a hightemperature can be cooled by nitrogen gas purging of the standby chamber33. When the temperature of this processed wafer 1 has fallen to atemperature that allows handling by the transfer device, the processedwafer 1 group is removed from the boat 21 by the wafer transfer device.The air in the standby chamber 33 is purged by nitrogen gas at thistime, so the formation of a natural oxidized film on the processed wafer1 is prevented, and the task of wafer discharge can be performed underatmospheric pressure. The film-forming process is repeated from hereonward by repeating each of the above steps.

In the above described film-forming process, during the boat loading ofthe wafer 1 into the processing chamber 14 with the temperaturemaintained at the process temperature, the temperature of the wafer 1rises on the periphery on the side nearer the heater unit 30 and riseslater in the center section on the side farther away from the heaterunit. Due to the relation between the temperature differential withinthe surface of this wafer 1 and the weight of the wafer 1 itself, aphenomenon occurs where the wafer 1 curves into a concave shape (shapewhere the center section drops and periphery rises). Along with thecurvature of the wafer 1, the support surface 26 of the support groove25 of the boat 21 and the supported surface on the periphery on thelower surface of the wafer 1 rub against each other, causing the weakfilm on the boat 21 formed in the previous film-forming process to peel.The peeled film becomes particles that fall from the support surface 26of the support groove 25, and adhere to the upper surface which is thesurface where the IC is fabricated on the wafer 1 directly below so thatthese particles cause lower productivity in the IC manufacturing method.

However, in the present embodiment, the wafer 1 is supported above thesupport surface 26 by the protrusion 28 formed in the center section ofthe support surface 26 of the support groove 25 so that even if peelingof the film occurs due to friction between the supported surface of thewafer 1 and the protrusion 28 of the boat 21, the particles resultingfrom the peeling are prevented from dropping onto the wafer because theparticles are caught by the support surface 26 of the boat 21. In otherwords, even if peeling of the film occurs due to friction between thesupported surface of the wafer 1 and the protrusion 28 on the boat 21,the particles resulting from the peeling are prevented from attaching tothe upper surface directly below which is the surface on the wafer 1where the IC is fabricated. Consequently a drop in productivity in theIC manufacturing method due to the generation of particles can beprevented. The support surface 26 therefore is a receiving section forcatching the particles generated by the protrusion 28 which is thesupport section supporting the wafer 1.

FIG. 4 is a graph showing the interrelation of the shape of the supportsurface and the increased quantity of particles. Here, the increasedparticle quantity signifies the increase in particles after processingversus the particle quantity prior to processing. In FIG. 4, thevertical axis is the increase in the number of particles of 0.16micrometers, while the horizontal axis shows the case of the prior artwithout the protrusion, and the case of the present embodimentpossessing the protrusion. In each case, the TOP bar indicates theincreased number of particles in the top section of the boat, and theBOTTOM bar indicates the increased number of particles in the bottomsection of the boat. The test conditions were identical for each case.The temperature in the processing section 14 in the boat loading stepwas set to 530° C. The pressure in the standby chamber 33 and theprocessing chamber 14 was set to 200 Pa. As can be understood from FIG.4, in the present embodiment, the increase in particle quantity for boththe top and bottom sections was reduced to less than 20 particles.

FIGS. 5 a and 5 b are drawings showing the particle distribution. FIG. 5a is a drawing showing the case of the prior art with no protrusion.FIG. 5 b is the case of the embodiment, possessing a protrusion. In thecase of the prior art not having a protrusion as shown in FIG. 5 a,there are particles present unevenly distributed in the sectioncorresponding to the holding member 24. In contrast, in the case of theembodiment possessing the protrusion shown in FIG. 5 b, the particlesare not unevenly distributed in the section corresponding to the holdingmember 24, and are spread over the entire section. This exampledemonstrates that the particles are being caught by the support surface26 and are not dropping onto the upper surface of the wafer 1.

However, in the boat loading step, the quantity of particles generatedbecomes larger, the lower the pressure in the standby chamber and theprocessing chamber. The quantity of particles generated becomes smalleras the pressure becomes higher. In the case in FIG. 4, the pressure inthe standby chamber 33 and the processing chamber 4 in the boat loadingstep is set low at 200 Pa, however the number of increased particles waslimited to 20 or less. Therefore, the pressure in the standby chamber 33and the processing chamber 14 in the boat loading step for theembodiment is preferably set to 200 Pa or higher.

However, setting the pressure in the standby chamber 33 and theprocessing chamber 14 high excessively in the boat loading step, causesa long pressure adjustment time due to the large differential versus theprocess pressure in the processing step (110 Pa in the presentembodiment). Also, setting the pressure too high does not allowadequately suppressing the increase in natural oxidized film. When thepressure in the boat loading step is for example set to atmosphericpressure (approximately 1013 hPa) which is a comparatively highpressure, time is required to adjust the pressure which exerts adverseeffects on the throughput and moreover, the natural oxidized film cannotbe adequately suppressed. Therefore a pressure lower than atmosphericpressure, for example 3000 Pa or less is preferable for the standbychamber 33 and the processing chamber 14 in the boat loading step. Ifset to a pressure lower than atmospheric pressure, preferably 3000 Pa orless, then the time needed for pressure adjustment from boat loadingstep to the process step can be set to the time that will not exert aneffect on throughput. Another benefit is that the generation of thenatural oxidizing layer can be adequately suppressed. In other words,the pressure in the standby chamber 33 and the processing chamber 14 inthe boat loading step should be 200 Pa or more and below atmosphericpressure, and preferably is set to 200 Pa or more and 3000 Pa or less.

The above described embodiment yields the following effects.

(1) The wafer is supported in an upward state from the support surfaceby the protrusion formed in the center of the support surface of thesupport groove so that even if peeling of the deposited film occurs dueto the friction generated between the protrusion on the boat and thesupported surface of the wafer, the particles resulting from the peelingare caught by support surface of the boat and therefore the falling ofparticles onto the wafer can be prevented.

(2) Even if peeling occurs due to friction occurring between theprotrusion on the boat and the supported surface of the wafer, theparticles resulting from the peeling can be prevented from adhering tothe upper surface of the wafer directly below on which the IC is formedso that a drop in production in the IC manufacturing method due to thegeneration of particles can be prevented.

(3) By setting the pressure in the standby chamber and the processingchamber in the boat loading step to 200 Pa or more and below atmosphericpressure, and preferably setting it between 200 Pa or more and 3000 Paor less, the adjustment time required during pressure adjustment fromboat loading step to the process step can be set to the time that willnot exert effects on the throughput, the generation of a naturaloxidizing layer can be adequately suppressed so that a drop in thethroughput is prevented and the formation of a natural oxidizing layercan definitely be prevented.

FIG. 7 is a perspective view showing the support groove section of theboat for the CVD apparatus of the second embodiment of the presentinvention. FIG. 8 is a timing chart showing the pressure in the filmforming process for the IC manufacturing method of the second embodimentof the present invention. FIG. 9 is a graph showing the relation of anincreased particle quantity to the size of the receiving section. FIG.10 is a drawing comparing the respective receiving sections used in theexperiment. FIGS. 11 a and 11 b are distribution graphs showing theeffect on reducing particle.

In this embodiment as shown in FIG. 7, the support section 28A thatcontacts and supports the bottom edge of the wafer 1 on the supportgroove 25 section in the holding member 24 of the boat 21 is providedhorizontally inwardly along the radius of the wafer 1. Below the supportsection 28 A is the receiving section 26A for catching the particlesgenerated by the support section 28A. The receiving section 26A isformed horizontally inwardly along the radius of the wafer 1 so as toextend outwards in three directions from the outer periphery of thesupport section 28A, in other words, the outer periphery of the supportsection 28A which is not in contact with the main pillar section of theholding member 24. The support section 28A uses the same material as theholding member 24 and is formed in a right-angled parallel piped shapeas seen in a plan view. The receiving section 26A uses the same materialas the support section 28A and is formed in a flat plate in the shape ofa square as seen from a plan view. The extension quantity L (distance Lfrom the edge of the support section 28A shown in FIG. 7 to the edge ofthe receiving section 26A) or in other words the distance that thereceiving section 26A extends outwards in three directions from theouter periphery of the support section 28A not contacting the mainpillar section of the holding member 24, is six millimeters or more, andpreferably is set between 6 and 15 millimeters.

The film-forming process for the IC manufacturing method of the secondembodiment of the present invention using the CVD apparatus containingthe boat structured as explained above, is described next in FIG. 8using the forming of a silicon nitride (Si₃N₄) film on the wafer as anexample.

In the wafer charging step where multiple wafers 1 are loaded in theboat 21, as shown in FIG. 8 a, the pressure in the standby chamber 33 ismaintained at atmospheric pressure (approximately 1013 hPa) by purgingthe air in the standby chamber 33 with nitrogen gas. This nitrogen gaspurge of the standby chamber 33 prevents the formation of a naturaloxidized layer on the wafers 1, and the wafer charging task is performedunder atmospheric pressure.

In the boat loading step where the boat 21 installed with a specifiednumber of wafers 1 is loaded into the processing chamber 14, as shown inFIG. 8 a, the pressure in the standby chamber 33 is depressurized to 200Pa and maintained there. The pressure in the processing chamber 14 isalso maintained at 200 Pa as shown in FIG. 8 b. The temperature in theprocessing chamber 14 at this time is regulated so as to maintain750.degree. C. of the heat treatment temperature, however thistemperature drops somewhat when the boat 21 is loaded inside.

In the processing step for processing the wafer 1 group supported in theboat 21, as shown in FIG. 8 b, the pressure in the processing chamber 14is depressurized to 30 Pa. In this case, the pressure in the standbychamber 33 is maintained at 200 Pa. Next, dichlorosilane (SiH₂Cl₂) gasand ammonia (NH₃) as the process gas are supplied to the processingchamber 14 and a silicon nitride (Si₃N₄) film is deposited on the wafer1. In the boat unloading step after the preset processing time haselapsed, as shown in FIG. 8 a, the pressure of the processing chamber 14is increased to 200 Pa, approximately the same as the pressure in thestandby chamber 33 maintained at 200 Pa. Performing the boat loadingstep while maintaining a low pressure such as 200 Pa is extremelyeffective in preventing the formation of a natural oxidized film on thewafer 1 that has been processed.

In the wafer discharging step where the processed wafer 1 is removedfrom the boat 21 that was loaded in the standby chamber 33, as shown inFIG. 8 a, the air in the standby chamber 33 is purged by nitrogen gas sothat the pressure in the standby chamber 33 is increased to atmosphericpressure and maintained there. The processed wafer 1 that has reached ahigh temperature can be force cooled by nitrogen gas purging of thestandby chamber 33. When the temperature of this processed wafer 1 hasfallen to a temperature that allows handling by the transfer device, theprocessed wafer 1 group is removed from the boat 21 by the wafertransfer device. The air in the standby chamber 33 is purged by nitrogengas at this time so the formation of a natural oxidized film on theprocessed wafer 1 is prevented, and the task of wafer discharge can beperformed under atmospheric pressure. The film-forming process isrepeated from here onward by repeating each of the above steps.

In the above described film-forming process, during the loading of theboat with the wafers 1 into the processing chamber 14 maintained at theprocess temperature, the temperature of the wafer 1 rises on theperiphery on the side nearer the heater unit 30 and rises later in thecenter section on the side farther away from the heater unit. Due to therelation between the temperature differential within the surface of thewafer 1 and the weight of the wafer 1 itself, a phenomenon occurs wherethe wafer 1 curves into a concave shape (shape where the center sectiondrops and periphery rises). Along with the curvature of the wafer 1, thesupport section 28A of the boat 21 and the supported surface on theperiphery on the bottom surface of the wafer 1 rub against each other,causing the weak film on the boat 21 formed in the previous film-formingprocess to peel and drop. The dropped particles are caught by thereceiving section 26A below the support section 28A so that theparticles do not drop onto the wafer. In other words, even if peeling ofthe film occurs due to friction between the supported surface of thewafer 1 and the support section 28A of the boat 21, the particlesresulting from the peeling are prevented from attaching to the uppersurface directly below which is the surface on the wafer 1 where the ICis fabricated. Consequently a drop in productivity in the ICmanufacturing method due to the generation of particles can beprevented.

FIG. 9 is a graph showing the relation of an increased particle quantityto the size of the receiving section. Here, the increased particlequantity signifies the increase in particles after processing versus theparticle quantity prior to processing. In FIG. 9, the vertical axis isthe increase in the number of particles in excess of 0.2 micrometers,while the horizontal axis shows the example of the prior art, and theexample present embodiment as shown in FIG. 10. The test conditions wereidentical for each case. The temperature in the processing chamber 14 inthe boat loading step was set to 750° C. The pressure in the standbychamber 33 and the processing chamber 14 was set to 200 Pa.

FIG. 9 shows that though the increased particle quantity was 133particles in the case of the prior art, the increased particle quantityfor the first embodiment, second embodiment, third embodiment, andfourth embodiment were respectively 45 particles, 22 particles, 10particles, and 11 particles and were in all cases 45 particles or less.In other words, the increased particle quantity can be reduced to 45particles or less by setting the extension quantity L from the corner onthe side of the tip of the support piece 28A of the receiving section26A to two millimeters or more. Also, the increased particle quantitycan be reduced to 20 particles or less if the extension quantity L ofthe receiving section 26A is set to six millimeters or more. Setting theextension quantity L of the receiving section 26A to ten millimeters ormore can reduce the increased particle quantity to about 10 particles orless. As clearly shown by comparing the third embodiment and the fourthembodiment, the particle reduction effect is saturated in the case ofthe fourth embodiment where the extension quantity L of the receivingsection 26A is 15 millimeters. In other words, the extension quantity Lfrom the outer edge of the support section 28A of the receiving section26A is preferably set from 2 to 15 millimeters. Even more preferable issetting the extension quantity L from 6 to 15 millimeters.

FIGS. 11 a and 11 b are drawings showing the particle distribution. FIG.11 a shows the example of the prior art of FIG. 10 without the receivingsection. FIG. 11 b shows the case of the fourth embodiment of FIG. 10.In the case of the prior art shown in FIG. 11 a, there are particlespresent that are unevenly distributed in the section corresponding tothe holding member 24. In contrast, in the case of the fourth embodimentshown in FIG. 11 b, the particles are not unevenly distributed in thesection corresponding to the holding member 24, and are spread over theentire section. This example demonstrates that the particles are beingcaught by the receiving section 26A and therefore are probably notdropping onto the upper surface of the wafer 1.

The present embodiment as described above therefore also renders thesame effect at the previous embodiment.

FIGS. 12 a, 12 b and 12 c are drawings showing a portion of the supportgroove on the boat for the CVD apparatus of the third embodiment of thepresent invention. FIG. 12 a is a perspective view. FIG. 12 b is a plancross sectional view. FIG. 12C is a frontal cross sectional view.

In this embodiment, the boat is comprised of multiple holding members,in this case three members, the same as in the first embodiment and thesecond embodiment. As shown in FIGS. 12 a, 12 b and 12 c, the holdingmember 24B of the boat 21 of the present embodiment is a columnar shape.The support groove 25B is formed by machining on the section towards thecenter of the wafer 1 on the outer circumferential surface of theholding member 24B. The support section 28B contacting and supportingthe lower surface of the wafer 1 on the support groove 25B is formedfacing inwards horizontally along the radial direction of the wafer 1.The receiving section 26B for catching the particles generated on thesupport section 28B is formed across the entire edge of the supportsection 28B at a position lower than the support section 28B (below thesupport section 28B). The support section 28B has a mountain shape asseen from a plan view. More accurately, the support section 28B has aflat trapezoidal shape. The peak or in other words, the upper base(shorter side) of this trapezoid points towards the center of the wafer1 and the lower section of the mountain or in other words the lower base(longer side) of the trapezoid is formed facing side opposite the centerside of the wafer 1. In other words, the width of the support section28B shape becomes narrower as it approaches the center of the wafer 1from the columnar section of the holding member 24B shown by the hatchmarks in FIG. 12 b. The upper base section of the trapezoidal shape ofthe support section 28B where the wafer is placed is roundly chamfered.The support section 28B of trapezoidal shape can be formed at the sametime that the support groove 25B is being cut-machined. The shape of thereceiving section 26B as seen from a plan view, is a shape cut the crosssectional shape of a section of the column shown by the hatching in FIG.12 b and the trapezoidal shape of the support section 28B from thecircular cross section of the receiving section 26B of the holdingmember 24B. The receiving section 26B is continuously formed from thesection of the column of the holding member 24B to the edge of thesupport section 28B (two oblique sides and upper base of the trapezoid).The receiving section 26B can be formed at the same time that thesupport section 28B and the support groove 25 b on the holding member24B is being cut-machined.

Besides the effects of the previously described embodiments, the presentembodiment also yields the following effects. The number of machiningsteps can be reduced since the receiving section 26B and the supportsection 28B can be formed simultaneously just by cut-machining thesupport groove 25B on the holding member 24B. The number of parts canalso be reduced by integrating the support section 28B, the receivingsection 26B and the holding member 24B into one piece, and therefore thecost of CVD apparatus production can be lowered as well as the boat. Thecut-machining of the holding member 24B is simple since the supportsection 28B is a plate shaped trapezoid as seen from a plan view andformed so that the width narrows towards the center of the wafer 1.Further, the mechanical strength of the holding member 24B is maintainedand the contact surface area with the wafer can therefore be reduced. Inother words, not only is the boat easy to machine, but the boat is alsomaintained at an ample structural strength while supporting the weightof the wafer, and at the same time the extent of contamination due tocontact with the rear surface of the wafer can be lowered by reducingthe size of the contact surface area with the wafer.

The present invention is in no way or manner restricted by theembodiments and variations of all types that do not depart from theoverall concept may of course be implemented.

The present invention for example is not limited to a film-formingprocess for doped polysilicon film or silicon nitride film, and may alsobe applied to non-doped polysilicon film, non-doped amorphous siliconfilm, doped amorphous silicon film, silicon oxide film, and further maybe applied to film-forming process implemented by CVD apparatus for suchas metallic oxidized films such as tantalum oxide film, zirconium oxidefilm, etc. Particularly, the present invention is preferable whenforming a film by CVD, since the adverse effects from peeling of thefilm deposited on the support section of the boat in the prior processcan be prevented.

The semiconductor manufacturing apparatus for implementing theproperties of the semiconductor device manufacturing method are notlimited to the batch mode vertical hot-wall depressurization CVDapparatus having a process tube comprised of an outer tube and an innertube, and may be other CVD apparatus such as a single wafer CVDapparatus or a CVD apparatus comprised of a process tube having only anouter tube, and may be a heat treatment apparatus for implementing alltypes of thermal processes.

The embodiments of the present invention described the implementing ofwafer processing but processing may also be performed on photo masks,printed circuit boards, liquid crystal panels, compact disks andmagnetic disks, etc.

INDUSTRIAL APPLICABILITY

The present invention as described above, can prevent a drop inproductivity due to particles from the supported surface of a substratein a depressurized state.

1. A substrate support member for supporting substrates during heattreatment, wherein said substrate support member comprises multipleholding members installed vertically, each of said holding members hasmultiple support grooves, each of said support grooves contains asupport section to contact a substrate, and a receiving section formed,in a flat plate with a rectangular shape as seen from a plan view, belowsaid support section and extending outwards from a section of the outerperiphery of said support section, and said receiving section extendsoutwards to 6 mm or more from a section of the outer periphery of saidsupport section.
 2. A substrate support member according to claim 1,wherein said receiving section extends outwards between 6 mm and 15 mmfrom the section of the outer periphery of said support section.
 3. Thesubstrate support member according to claim 1, wherein said receivingsection extends outwards to 10 mm or more from the section of the outerperiphery of said support section.
 4. The substrate support memberaccording to claim 1, wherein said receiving section extends outwardsbetween 10 mm and 15 mm from the section of the outer periphery of saidsupport section.
 5. The substrate support member according to claim 1,wherein said support section is formed in a right-angled parallel-pipedshape with a rectangular shape as seen from a plan view, and saidreceiving section is formed in a flat plate with a rectangular shape asseen from a plan view.
 6. The substrate support member according toclaim 1, wherein said support section is arranged inside the outerperiphery of said receiving section as seen from a plan view.
 7. Asubstrate support member for supporting substrates during heattreatment, wherein said substrate support member comprises multipleholding members installed vertically, each of said holding members hasmultiple support grooves, each of said support grooves contains asupport section to contact a substrate, and a receiving section, formedin a flat plate below said support section and extending outwards from asection of the outer periphery of said support section, said supportsection is formed in a flat plate with a trapezoid as seen from a planview, and the shorter side of the pair of parallel sides of thetrapezoid faces the center of said substrate.
 8. The substrate supportmember according to claim 7, wherein said support section is formed in aflat plate with a trapezoid as seen from a plan view, and a shorter sideof a pair of parallel sides of the trapezoid faces the center of saidsubstrate, and a longer side of a pair of parallel sides of thetrapezoid faces side opposite to the center of said substrate.
 9. Thesubstrate support member according to claim 7, wherein said supportsection is arranged inside the outer periphery of said receiving sectionas seen from a plan view.
 10. The substrate support member according toclaim 7, wherein said receiving section is formed as a flat plate with acircular shape as seen from a plan view.
 11. The substrate supportmember according to claim 7, wherein each of said holding members has acolumnar shape.
 12. A substrate support member for supporting substratesduring heat treatment, wherein said substrate support member comprisesmultiple holding members installed vertically, each of said holdingmembers has multiple support grooves, each of said support groovescontains a support section to contact a substrate, and a receivingsection formed in a flat plate below said support section and extendingoutwards from a section of the outer periphery of said support section,said support section is formed in a flat plate with a trapezoidal shapeas seen from a plan view, and the width of said support section becomesnarrower as it approaches the center of said substrate.
 13. Thesubstrate support member according to claim 12, wherein said supportsection is arranged inside the outer periphery of said receiving sectionas seen from a plan view.
 14. The substrate support member according toclaim 12, wherein said receiving section is formed as a flat plate witha circular shape as seen from a plan view.
 15. The substrate supportmember according to claim 12, wherein each of said holding members has acolumnar shape.